"Cell Phones Don’t Increase Cancer Risk in Kids." From USA Today to CBS News, variations of this hopeful-sounding headline now abound after yesterday's release of a new study in the Journal of the National Cancer Institute.

But experts have some serious concerns regarding the methods and conclusions of the first study evaluating the connection between cell phone radiation and brain cancer in children and teens. Not only was the study flawed, they note, but it was also financially supported by the cell phone industry.

"To have moms assume that kids using cell phones are safe is the wrong conclusion to make," Devra Davis, president and founder of the consumer advocacy group Environmental Health Trust, told The Huffington Post.

After looking at brain tumors and cell phone use among about 1,000 boys and girls between the ages of 7 and 19, European researchers determined that kids who averaged one or more weekly cell phone calls over a period of at least six months were not at an increased risk of developing a brain tumor compared to peers that were non-users. Overall, less than 15 percent of the children and teens had spent more than 4 years as a cell phone user.

"It’s ridiculous to think that because you didn’t find a significant increase in brain cancer among kids that now cell phones are safe," added Davis. She likened the study to looking at 16-year-olds who smoked as children to see if they had lung cancer. “You’d find nothing,” she said.

Dr. Keith Black, a brain tumor expert at Cedars-Sinai in Los Angeles, agreed. "It usually takes decades of exposure for a person to be at an increased cancer risk," he told The Huffington Post, adding that the extent of the exposure observed in the study was extremely small.

"It's interesting that most of the studies that have shown a correlation between brain cancer and cell phone use have tended to look at long-term exposure -- at least 10 years -- and at higher doses such as using a cell phone for 60 minutes or more each day," said Dr. Black. "Studies that have tended to not find a link looked at short-term use -- maybe an hour or so a month."

Unlike ionizing radiation such as X-rays or gamma rays, which are strong enough to damage the DNA in cells, far less is known about the cancer-causing potential of radiofrequency waves emitted by cell phones. What's more, most of the studies thus far have only looked at adults. Adults, however, absorb about half as much radiation while using one of the devices compared to children.

The latest addition to the conflicting assortment of studies was partially supported by money from mobile communication companies. However, senior author Martin Roosli of the Swiss Tropical and Public Health Institute in Basel, Switzerland, told HuffPost that the industry "did not have any say" in how the study was conducted. The author of an accompanying editorial that affirmed the finding is employed at the International Epidemiology Institute, which has reportedly received funding from the telecommunications industry.

Published yesterday, the study also comes on the heels of Tuesday's unanimous ruling in San Francisco that will soon require all local cellular retailers to post radiation exposure warnings on every phone and hand every customer education material. The city's mayor is expected to sign the ruling into law within the next week, with more cities likely to follow San Francisco's lead, according to Ellen Marks, director of government and public affairs for Environmental Health Trust. Berkeley, Philadelphia and New York City are among those looking to impose similar legislation.

In an interview with The Huffington Post, Marks suggested that cities had been waiting to see how San Francisco fared. Their legislation had been previously tabled after a lawsuit from the cell phone industry, which claimed that the measure violated their first amendment rights.

"But it’s in very fine print and hidden in a manual. Nobody reads them," she said. "People have right to information to make safe choices."

Roosli acknowledged that some uncertainty still remains concerning more intense cell phone use over longer-time periods. "We studied mobile phone use as reflective of the early 2000s. At that time it was quite expensive for young people and most did not use mobile phones a lot," he said. "So things might have changed."

Still, he maintained that the study "does not indicate that there is some major risk" and that people "can be quite confident that less than five years of moderate mobile phone use does not cause cancer."

The World Health Organization (WHO) came to a different conclusion after evaluating the evidence. They determined that mobile phones are a "possible carcinogen," listing use of the devices in the same category as lead, engine exhaust and chloroform, CNN reported.

Both Dr. Black and Davis admitted that they still own two cell phones each, but are careful to use a headset or speakerphone, and only make calls in areas with good reception.

"The best thing is to simply get in the habit of turning your phone off," added Davis, emphasizing the importance of these precautions for kids. "Do you really want to run an experiment on your children like we did with tobacco?"